Optical scanning unit for mark sensing

ABSTRACT

Optical-scanning system for a mark sensing unit wherein a laser beam is deflected through a predetermined arc to traverse a predetermined lineal distance on a record disposed chordally with respect thereto. A beam-splitting device disposed adjacent to the scanned surface directs a portion of the laser beam through an auxiliary clocking grid having a series of apertures sized and spaced in complemental accord with the format of the document being scanned. The varying intensity pattern produced by the passage of the split beam along the clocking grid is converted into a sequence of discrete electrical signals that is readily correlatable with other electrical signals that represent the presence or absence by marks on the scanned document as evidenced by intensity variation induced by the passage of the laser beam therepast to thereby provide a direct and accurate indication of beam location at all times independent of the nature of its displacement.

United States Patent Edward Camp Tibbals, Jr.;

[21] Appl. No. 636,204 [22] Filed May 4, 1967 [45] Patented July 27,1971 [73] Assignee Alexander, Inc.

Mlhwlh, NJ.

[54] OPTICAL SCANNING UNIT FOR MARK SENSING 2 Claims, 7 Drawing Figs.

52 us. Cl. ..235/61.I1E,

250/219 D, 350/99 [51] Int. Cl ..GOIn21/30, G02b 5/12, 006k 7/00 [50]Field oiSearchW 235/61.11, 61.l15',250/2191DC,219 ID, 217 $81.; 350/99X, 96, 113; l78/7.1, 7.6

[56] References Cited UNITED STATES PATENTS 2,297,851 10/1942 Wyss350/96 3,060,319 10/1962 Greunke. 250/2191DC 3,433,933 3/1969 Hardin250/2191D X 3,443,109 5/1969 Broom et a1. 250/2191D X 3,463,882 8/1969Herbold 178/7.1

OTHER REFERENCES Rohland, Multi-lnput, Optical Scanning Data Collection2 Terminal IBM Technical Disclosure Bulletin, Vol. 8, No. 10, March1966, pg. 1405 & 1406 ABSTRACT: Optical-scanning system for a marksensing unit wherein a laser beam is deflected through a predeterminedarc to traverse a predetermined lineal distance on a record disposedchordally with respect thereto. A beam-splitting device disposedadjacent to the scanned surface directs a portion of the laser beamthrough an auxiliary clocking grid having a series of apertures sizedand spaced in complemental accord with the format of the document beingscanned. The varying intensity pattern produced by the passage of thesplit beam along the clocking grid is, converted into a sequence ofdiscrete electrical signals that is readily correlatable with otherelectrical signals that represent the presence or absence by marks onthe scanned document as evidenced by intensity variation induced by thepassage of the laser beam therepast to thereby provide a direct andaccurate indication of beam location at all times independent of thenature of its displacement.

PATENTEU JUL27 197i SHEEI 1 [IF 3 INVENTORS EDWARD CAMP TIBBALS JF mgvoRTEMPLE 4/ r A T TORNE Y OPTICAL SCANNING UNIT FOR MARK SENSING Thisapplication relates to an improved scanning system for data recognitionand conversion of form thereof, and in particular to improvedconstructions for optical mark sensingtype data scanning and conversionunits for provision of coded input information for electronic computersand the like.

The preparation of input data for electronic computers, because of itscontinuing and redundant nature, oftentimes limits the inherentadvantage and diversity of computer use. In particular, the preparationof computer input materials which involve the human conversion ofvisually observed written data to a digital input code, with itsinherent speed limitation and high error probability, presents continualproblems. These problems are particularly acute in the processing ofmerchandise orders, inventory control and other similar endeavorsinvolving the handling of great numbers of discrete documents and greatmasses of diverse information derived from handwritten notationsthereon.

This invention may be briefly described an an improved optical-scanningsystem for character recognition and code conversion purposes that isparticularly adapted for the conversion of data represented byselectively located marks on printed forms into digitally encodedintelligence for a computer input. In its broad aspect the subjectinvention contemplates the patterned scanning of an intelligence bearingrecord sheet by a beam of monochromatic light with continuously operablesimultaneous coordination of sensed data and beam location for directconversion of the desired intelligence into digitally encoded form. Inits more narrow aspects the subject invention includes the patternedscanning of a record sheet bearing selectively located marks thereonrepresentative of the desired intelligence by a portion of a split laserbeam conjointly with the scanning of a selectively prepatternedpositioning grid by a second portion of said laser beam and theconversion of electrical signals representative of variations inreflected light from both said portions of said beam into a digital coderepresentative of the desired intelligence.

Among the advantages of the herein described system is, apart from theprovision ofa relatively simple and inexpensive mark-sensing system, apermitted increase in the information packing density on a scannablerecord, a selective response limited to marked patterns on the recordsheet and concomitant ability to distinguish the same from othervisually observable printed matter thereon, increased reliability of thesensed intelligence as occasioned by a marked increase in signal tonoise ratio for the sensed signals as well as a per mitted increase inboth speed and accuracy of scanning and conversion through utilizationof a simplified beam reflection system employing a reduced power lightsource. Still another advantage of the subject invention is theprovision of a marksensing unit of improved character utilizing areduced power light source and a markedly reduced number ofphotosensitive elements. A further advantage of the invention is theprovision of a mark-sensing unit having a high order of reliability andlowered manufacturing costs.

The object of this invention is the provision of a relatively simple andinexpensive mark-sensing system that is free of most, if not effectivelyall, of the liabilities normally attendant paper positioning and ensuingcomplications that characterize optical-scanning systems in existingequipment Other objects and advantages of the subject invention will beset forth in the following specification and will be apparent from theaccompanying drawings which illustrate the essentials of a presentlypreferred construction for a mark-sensing device incorporating theprinciples ofthis invention.

Referring to the drawings:

H6. 1 is an oblique view schematically showing, in somewhat idealizedform, the essential components ofa mark sensing system incorporating theprinciples of this invention.

FIG. 2 is a schematic front elevational view illustrating the operativepositional relationship of the major components includable in apresently preferred embodiment of this invention.

FIG. 3 is a sectional view as taken on the line 3-3 of FIG. 2.

FIG. 4 is a fragmentary plan view of a hypothetical order formillustrating the use of a IO-digit line and a six column block of ninedigit lines.

FIG. 5 is a fragmentary plan view illustrating a portion of a printedform having a plurality of markings disposed thereon for explanatorypurposes in conjunction with the operation of the subject system andadditionally schematically showing the relationship of the clocking gridto the form format.

FIG. 6 is a timing chart illustrating the various wave forms extantwithin the electronic components ofthe subject device.

FIG. 7 is a schematic block diagram of the suitable logic circuitryemployable in the practice of this invention.

Referring to the drawings and initially to FIG. 1, the subject inventionbroadly includes the utilization of a sharply focused beam ofmonochromatic light A as emitted from a laser source B which is lineallydeflected, as by a moving mirror C, to traverse a linear path across apredetermined scanning distance D as determined by the width ofadocument E being scanned. Disposed intermediate the document E and themirror C and angularly disposed adjacent the document surface is a beamsplitting mirror F which functions to deflect a portion of the movingbeam A through an auxiliary beam locating grid G having a series ofdiscrete spaced openings therein corresponding. in a predeterminedmanner to the document format and, conjointly therewith, to transmit theremaining portion of the beam A onto the surface of the document beingscanned. The area of the document being scanned is substantiallyenclosed by an elliptically shaped mark-sensing light hood H adapted tocollect and focus a substantial portion of the light diffusely reflectedfrom the document surface for activation of a photosensitive sensorelement J through a selective filter K.

Disposed on the remote side of the beam-locating grid G is a secondlight hood L adapted to collect the light rays that pass through theapertures in the clocking grid for activation of a second photosensitivesensor element M. Delineation of the finish location for the scanningtraverse of the beam A is effected by an auxiliary sensing device suchas an end of scan sensor 0 appropriately positioned relative to themargins of the document being scanned. The document E being scanned issupported upon a roller table P or other suitable means for locating thesame relative to the path of scan and to advance the same intermediateeach scanning traverse. Auxiliary sensing means, such as a positionsensor R is located adjacent the document margin and the longitudinalcode marks S thereon so as to provide signals indicative of thelongitudinal portion of the document to be scanned by the beam A.

FIG. 4 illustrates a suitable format for a preprinted order form or thelike that is readily scannable by this invention. Such form includes amarginal portion 26 bearing the printed firm name or logotype or otherindicia. Disposed therebeneath is an address or customer identificationsection 27 comprising, for example, a preprinted grid made up of two ormore transverse lines each including six columns of IO-digit rows. Underthe address section 27 is an array of order sections 29 headed by aspace 28 for visual identifying indicia in printed form. The ordersection 29 is constituted by a preprinted grid defining multiline blocksof six column groups of nine digit rows, each double block accommodatingmarkings representative of quantities of from 1 to 99. The left-handmarginal edge includes selectively located marks 25 for selective lineidentification and for initiation of scan. As will be now apparent, asalesman, for example, will prepare the order by introducing selectivelylocated marks representative of customer identification in the addresssection 27 and representative of the numerical quantity of one or morearticles in the order section 29. Since monochromatic light is employedfor scanning, printed matter may be readily imprinted in the same areasthat are to receive the marks as long as the printing inks employed willreflect the laser beam light in the same manner as the base paper. Undersuch conditions the detector will not distinguish between the printedmatter and the paper. As such the system will thus be selectivelyresponsive only to the marked patterns thereon and will be possessed ofthe inherent ability to distinguish between the printed matter and suchmarked pattern.

FIG. 5 illustrates, for the purposes of example, the inclusion of marksin each of the six column, IO-digi't rows in one line delineated by theline mark 25a on an order form together with a segment of the beamlocating grid 15 disposed in geometric alignment therewith as the samewould be located during a scanning traverse of the line 250 from left toright by the laser beam.

As more clearly shown in FIGS. 2 and 3, there is provided a source ofmonochromatic light such as a continuous wave gas or crystal laser 1.The output laser beam 2 is desirably focused so as to provide a highintensity scanning spot having a beam diameter as small as 0.0l inchesby an auxiliary focusing means 12a. Such sharp focusing permits a highdegree of discrimination and detection of both small marks and marks ofminimal intensity definition. The laser beam 2 is reflected by anangularly displaceable mirror 3 mounted on the coil of a galvanometer 4or on a rotating element such as a motor shaft or the like. As indicatedby the angular sector 6, the angular displacement of the mirror 3effects a displacement of the laser beam through a predetermineddistance in a straight line across one line of the document 12 beingscanned and whose rate of displacement can be readily controlled byeither electric current or potential in the form of shaped pulsesapplied to the mirror drive unit. As will become apparent hereafter, therate of displacement or variations thereof are of no consequence in thesubject system. Located in the path oftraverse of the laser beam is anelongate beam splitting member 7, suitably a thinly silvered mirrorwhich is disposed closely adjacent to the surface of the document 12being scanned and at a predetermined angle with respect thereto. Theimpingement of the laser beam up on the beam splitter 7 results in thereflection of a portion 8 thereof through the beam locating gridassembly 15, which is so constituted as to provide a plurality ofselectively located rectangular apertures 15a defined by intermediatewebs 15b (see FIG. of predetermined dimension so as to correspond withthe particular columnar format of the document being scanned. Preferablyeach discrete area on the document to be scanned is matched to oneaperture and one each on the clocking grid. The portion 3 of thereflected ray directed through the grid is sequentially interrupted bythe web members 15b incorporated therein during its passage thereacrossto provide a predetermined pattern of varying light intensity on thedownstream side thereof. The grid 15 is preferably enclosed in a lightcollecting hood 152 which contains a filter 16 opening into a diffuselyreflectant integrating chamber 17 containing photosensitive element suchas an elongate photomultiplier tube 18. As will be apparent, the filter16 is so constituted as to pass only light corresponding in frequency tothe laser beam and such, in combination with the hood 15c and chamber17, minimizes, if not eliminates, the deleterious noise effects thatmight otherwise result from stray or random light impingement upon thephotomultiplier tube 18. The variations in light intensity on thedownstream side of the clocking grid 15 occasioned by the sweep of thebeam 8 therepast will complementally modulate the output of thephotomultiplier tube 18. The output of the photomultiplier tube 18constitutes a series alternating electrical pulses 42 (FIG. 6) with eachpositive peak thereof corresponding to the passage of the laser beamthrough a grid aperture and the adjacent negative peaks corresponding topassage of the beam past the adjacent web and, as such, provides aninternal clocking system which always digitally indicates the positionofthe laser beam with respect to all locations on the line of thedocument being read.

The clocking grid 15 may suitably comprise a readily replaceable unitsuch as a prepatterned strip of film or the like that has been preparedfor use with a particular document format. Such replaceability greatlywidens the potential utility of the subject scanning system since itprovides the ready capability of accommodating a multiplicity ofdifferent document formats on a single piece of equipment.

If two dimensional beam locations are desired such can be effected bymerely utilizing an additional beam splitter and clocking grid assemblywith apertures arranged perpendicularly to those of the primary system.One immediate application of such a dual unit system would be for thepurposes of character recognition wherein recognition is accomplished bycorrelating the X and Y coordinates of the character defining areas witha stored standard therefor. In such a system the vertical sweep would beoflimited length (as determined by letter height) but would require amuch higher rate of traverse. A suitable high-speed scanning system isdisclosed in copending application Ser. No. 664,877, filed Aug. 31,I967.

The other end remaining portion of the laser beam that passes throughthe beam splitter 7 strikes the surface of the document 12 being scannedafter its passage through a slit aperture 9 in an elliptically shapedlight collecting hood member 10 which substantially completely enclosesthe area of the document 12 being traversed by the laser beam. Suchlight, after striking the document surface at the other focus of theellipse is diffusely reflected therefrom and by measuring the totalhemispherical radiant energy as so diffusely reflected, the presence orabsence of a mark can be detected. To this end the elliptically shapedhood 10 contains a second elongate photomultiplier tube 14 located atone focus of the ellipse and surrounded by a filter 11 that selectivelypermits passage of only the laser frequency light therepast.

The output of the mark-sensing photomultiplier tube 14, which normallywill be at full current because of the maximum amount of light reflectedby the document surface, will drop as the laser beam passes over a markin its passage across the document, as illustrated by the wave form 43on FIG. 6.

As will now be apparent, the output of the mark sensing photomultiplier14, when correlated with the clocking signal emanating from thephotomultiplier 18 provides a composite signal that completelydelineates the intelligence of the information described on the documentby the pattern or placement of marks thereon.

As also shown on FIGS. 2 and 3 the unit includes a suitable paper driveassembly, schematically designated by the roller 19, to advance thedocument being scanned in a direction transverse to the path ofdisplacement of the laser beam to permit the sequential traverse ofsucceeding lines thereof. In order' to assure a fixed location for theportion of the document 12 being scanned by the laser beam, an elongatesuction chamber 20 connected by a pipe 21 to a source of partial vacuumunderlies a perforated document supporting platform or the like. Theidentity of the line 25 being scanned is indicated by the response of aphotocell 24 located to respond to light intensity variations caused bythe passage ofline marks 25 past a light source 22 and a beamconcentrating lens 23. The termination of the scanning traverse isdetected by means of an auxiliary mirror 31 angularly disposed to directthe laser beam into a second photocell 30. A separate sensing device,comprising light source 32, lens 33 and photocell 34, is disposedbeneath the scanned document to signal the completion of its passagepast the scanning location.

As will be apparent from line 43 on FIG. 6, the variations in markintensity, position and size of the deposited marks on the record willresult in signals emanating from the mark-sensing photomultiplier thatdepart from ideal pulse shape both in width and amplitude. Because,however, the information is of a digital nature, these irregular waveforms can be readily reshaped as shown in line 45 and subsequentlytreated in the electronic components so as to allow the informationrepresented thereby to be properly encoded in the system and correlatedwith the beam position signal resulting from the clocking grid. FIG. 6illustrates, in highly schematic block diagram form, the nature ofsuitable electronic components that are utilizable for handling of thedigital-type data produced by the above system. As there shown, theoutput signals of the mark-sensing photomultiplier tube 14 and theclocking tube 18 as well as the monopulse outputs of the auxiliaryphotocells 24, 30, and 34, are readily fed into respective amplifier andshaping unit 5054 respectively to convert the same into a formapproaching that of rectangular pulses. The squared clock pulse outputof the amplifier 51 is fed into a counterunit 55 which also is adaptedto receive the monopulse-type output of the mark-sensing signalamplifier 50. The counterunit 55 correlates these signals with relationto each other and feeds them into a code converting unit 56, forconversion of the correlated signals into a form convenient forintroduction of the converted data into a memory unit 57. As indicated,the signals emanating from the line clock photocell amplifier 52, theend of scan signal amplifier 53, and the end of order amplifier 54 arelikewise fed into the code conversion unit 56 for proper correlationwith the signals emanating from the counting unit 55 so as to properlyencode and correlate the information relative to each line of eachparticular order into the memory unit for subsequent readout ontomagnetic tape or other record.

As will be apparent to those skilled in this art, the particularelectronic circuitry and logic components required will be designed tomeet the exigencies of a particular order form and type of data requiredtherefrom and as pointed out earlier, may also include the necessarycircuits for discrimination and correction of errors associated with theincorrect mark placement and imperfect marks.

As will now be apparent from the foregoing the system is possessed of anumber of unique advantages, among which are (a) selective response toadded marks and concomitant ability to distinguish between printedmatter and marked patterns, (b) minimization of random noise in entrysignals to electronic components with enhanced reliability due togreater signal to noise ratio as so obtained, reduced power and expenseof both light source and in photosensitive components (d) permittedincrease in packing density of scannable information (e) simplicity ofconstruction with enhanced speed and accuracy and (f) avoidance ofanalog to digital conversion in the preparation of input computer data.

Having thus described my invention, we claim:

1. Optical-scanning apparatus comprising laser means for producing abeam of monochromatic light,

means for lineally deflecting said beam through a predetermined distancetransversely across the surface of a record to be scanned,

means to displace said record in a direction perpendicular to the pathof travel of said beam,

a light confining hood assembly extending over the path of travel ofsaid beam and containing means selectively responsive only to lightintensity variations induced by the passage of said beam overintelligence representing indicia located on said record surface forproviding first discrete electrical signals representative thereof,

clocking grid means disposed adjacent said record surface including amasking element defining a multiplicity of discrete apertures separatedby light impervious wall members for incrementally subdividing saidpredetermined distance into a predetermined number of discrete segmentsprepatterned in accord with the intelligence being scanned,

beam splitting means disposed adjacent to said record surface andextending over the path of travel of said lineally deflected beam fordirecting a portion of said beam through the masking element of saidclocking grid during the lineal deflection thereof through saidpredetermined distance,

and means responsive to the light intensity variations induced by thesequential blockage and passage of said portion of said beam throughsaid masking element during its traverse thereof for providing asequence of second discrete electrical signals selectivelyrepresentative of the location of said beam at all times during thetraverse of said record whereby correlation of said first electricalsignals with the

1. Optical-scanning apparatus comprising laser means for producing abeam of monochromatic light, means for lineally deflecting said beamthrough a predetermined distance transversely across the surface of arecord to be scanned, means to displace said record in a directionperpendicular to the path of travel of said beam, a light confining hoodassembly extending over the path of travel of said beam and containingmeans selectively responsive only to light intensity variations inducedby the passage of said beam over intelligence representing indicialocated on said record surface for providing first discrete electricalsignals representative thereof, clocking grid means disposed adjacentsaid record surface including a masking element defining a multiplicityof discrete apertures separated by light impervious wall members forincrementally subdividing said predetermined distance into apredetermined number of discrete segments prepatterned in accord withthe intelligence being scanned, beam splitting means disposed adjacentto said record surface and extending over the path of travel of saidlineally deflected beam for directing a portion of said beam through themasking element of said clocking grid during the lineal deflectionthereof through said predetermined distance, and means responsive to thelight intensity variations induced by the sequential blockage andpassage of said portion of said beam through said masking element duringits traverse thereof for providing a sequence of second discreteelectrical signals selectively representative of the location of saidbeam at all times during the traverse of said record whereby correlationof said first electrical signals with the complemental signals in saidsequence of second discrete signals defines the location and nature ofsaid intelligence representing indicia on said record. 2.Optical-scanning apparatus as set forth in claim 1 including means forsensing the location of the lineally deflected beam longitudinally ofsaid record to provide a third electrical signal indicative of thelocation thereof longitudinally of said record and operative with saidsecond electrical signals to provide a two-dimensional indication of thephysical location of said beam.